Dredging apparatus



Feb. 14, 1939.

L. s. ROSENER 2,147,062

DREDGING AEPARATUS Filed April 16, 1937 3 Sheets-Sheet l INVENTOR.

LELAND J. Boss-Nae arm/W 0;

A TTORNEY 1939- L. s. ROSENER 2,147,062

DREDGING APPARATUS Filed April 16, 1957 5 Sheets-Sheet 2 V INV R. LELAND 6'. EO'SENER A TTORNEY Patented Feb. 14, 1939 UNITED STATES PATENT OFFICE I DREDGING APPARATUS Leland S. Bonner, San Francisco, Calif.

Application April 18, 1937, Serial No. 137,218

Claims. (Cl. 31-49) My inventionrelates to dredging apparatus, more particularly to a bow-winch construction therefor.

In dredging apparatus,more specifically as it applies to the mining of gold in the sand and gravel deposits along the shores and the beds of shallow streams, all the apparatus necessary for the loading of the gold-containing material and the separation of the gold therefrom is mounted on the dredger itself. A ladder, supporting a bucket-line, at the front of the dredger maintains the buckets in a position to scoop'up the sand and gravel. The bucket-line carries'the gravel deposits to a height of approximately 25 or 30 feet above the deckof the dredger, where the contents of the buckets is dumped into a hopper, from which it is guided to a rotatable cylindrical screen supported at a substantial height above the deck, in line with the longitudinal axis thereof, and at an angle of approximately 17 with the horizontal. The gravel is sifted through the rotating screen, the sittings including the sand and gold particles mixed therewith, whereas the larger elements gradually travel toward the end of the screen, due to its angular position with the horizontaL'and drop into a small hopper, from which they are guided onto a stacker mechanism which piles the coarse gravel and stones to the rear of the dredge. The stacker device comprises an endless belt afiair mounted on a supporting frame which extends upwardly and rearwardly from the rear end of the dredger.

The sittings containing the gold content, tall upon riflie boards, which comprise surfaces inclined slightly toward the sides and rear of the dredger. These surfaces are provided with strips of material disposed at right angles to the normal flow of the sittings thereover. Mercury, scatteredover the riiiie board collects in small pools against the aforementioned strips and amalgamates with the gold particles as they'settle out of the sittings. The sand content, which is of lower specific gravity than gold, will for the most suitable spud, pile or other pivot element into the gravel bottom of the stream, and attaching the dredger thereto, to permit of a swin movement of the dredger about the spud or pile as a pivot point.

' The angular shift of the dredger is controlled by suitable lines or cables extending from some 5 point on the dredger, such as the top of the ladder, through pulleys or sheaves affixed to stakes or other fixed elements located at some distance to either'side of the dredger, either on shore or anchored in the bed of the stream, the cables then terminating at suitable winch apparatus mounted on the deck. The winch apparatus is so controllable as to exert a pulling effect from either side of the dredger to effect movement thereof in a selected direction, each cable or bow-line constituting a mechanical power transfer link, extending through a point which is fixed against movement, namely the pulley or sheave which is anchored to a spike or other element on shore.

The bucket-line and ladder support is adjustable vertically, to enable the buckets to take a deeper cut during. each transverse swing of the dredger, until bed rock is reached. The spud is then removed and the dredger moved forward in position to take another slice out of the shore line. When properly located, the spud is again driven into the bed of the stream at the rear end of the dredger and the dredging operations are repeated, with the dredger pivoted about the spud in its new location.

While the operation of the stacker mechanism tends to build up the shore line behind the dredger, the operation of the bucket line, besides its normal function of scooping-up the gravel deposits, serves to dig a channel ahead for the dredger. In effect, therefore, the dredger creates its own pond, which shifts with forward travel of the dredger.

The type of bow-winch apparatus in use prior to my invention, comprises a pair of drums located side by side with their axes in alignment, and with a shiftable clutch mechanism located between the two drums and adapted to engage a power drive and transfer the power selectively to either one or the other of the two drums, the power drive constituting an electric motor mechanically connected to the driving-element of the clutch. Each of the drums is provided adjacent its outer side with a hand-controlled braking mechanism.

Control of the winch apparatus is exercised manually from an operator's cabin, located approximately on the level of the screen and hopper mechanism above deck, and since the clutch and brakes onthewinchdmmsaretobeoperatedss brake control mechanism, extending from the clutch and brakes to the control cabin, it being noted that the control cabin is necessarily located at its high position above deck to enable an opparticular one depending on the desired direction in which the dredge is to shift, and the hand brake is adjusted on the other drum to effect a retarding action on the cable being unwound from that particular drum. When the dredger has reached the extreme end of its swing, the

brake is released, the clutch is shifted to engage the drum, which justpreviously was functioning as a retarding element, and the brake, on the w; drum which has just been disengaged from the hilt power drive, is adjusted to provide a drag against movement of the dredger in the opposite direction from that previously traversed. The speed of movement of the dredger is determined by the speed of the winding or take-up drum, which is the power driven drum, and the retarding or braking eifect of the other drum.

The bow-winch construction and operation just described as constituting the practice prior to my invention is subject to many deficflenciesj among which may beoutlined the following:

(1) By reason of the fact that the drums must be positioned adjacent each other in order to obtain the selectable clutching operation and adjustment of brakes, and in view of the fact that the clutch and brake control must be actuated from an operators cabin located above the deck, it becomes apparent that the location of the winch mechanism as to its position on deck is more or less pre-determined by these facts and the position of the screen and hopper mechanism, which would normally interfere with locating the clutch lever and brake control somewhere along the iongitudinal axis of the dredger. Since the location of the clutch control lever and brake controls determine the position of the control or operators cab, it follows, of necessity, that the operator must be positioned to one side of the dredge, at a position where his view of the dredging operations at times will be impaired by the presence of the bucket-line and supporting structure, and the hopper adjacent thereto. I

(2) In apparatus involving mechanical braking, periodic repairs and replacement of the brakebands or brake elements becomes necessary,

and this, besides contributing to the expenses of operation, is always accompanied by periods of shut-down. Frequent burning of the brakebands often necessitates interruption in operation of the winch apparatus.

(3) The energy generated in the braking process is transformed into heat, which performs no .useful work.

participate'in the dredge positioning operations.

Iri'the event that due to wear or otherwise, the driving cable or bow-line should break; and the dredge should relax its pull on the remaining cable, the inherent passive characteristic' of mechanical braking, will manifest itself in permit- 1 ting slack todevelop. Y.

() .The location of the winches, to one side of from this point, it necessitates a clutch'lever and the longitudinal axis of the dredger, necessitates stringing one of the bow-lines or cables across the dredger, up and over such apparatus as may be in the path, requiring a more involved pulley system or arrangement, and otherwise exposing the cable to greater opportunity for'wear and fouling.

The objects of my invention are to provide an improved bow-winch control apparatus which shall (1) Provide a constant re-wind torque to the braking winch, and therefore always take up whatever slack may tend to develop in its associated 'cable regardless of the cause therefor;

(2) Have no mechanical brakes, belts or clutches as necessary elements in the normal operation and control of thebow winch apparatus;

(3) Be electrically controlled and involve electrical braking as distinguished from mechanical braking;

.(4) Involve electrical braking which is regenerative in action;

(5) Involve braking apparatus, wherein the braking energy is converted into useful energy 'to reduce the overall expense of operation of the dredging apparatus;

(6) Incur an inappreciable amount of wear, with practically no replacements nor repairs in the braking mechanism;

(7) Involve smoother action and more positive speed control of the swinging movement of the dredger;

(8) Include self-protection against excessive overload conditions, which are normally apt to breakcation of the operator's cab to provide the operator with equal vision to either side of the bucketline;

(10) Permit of a symmetrical layout of the' bow-winch and control apparatus;

(11) Require less attention in the operation thereof and be more eillcient than the apparatus previously relied on and described above.

Additional objects of my invention will be brought out in. the following description of the same, taken in conjunction with the accompanying drawings, wherein a Fig. 1 and Fig. 2 are schematic views of a dredger, illustrating the general location of the main pieces of apparatus, including theimproved bow-winch of my invention, the illustration of Fig. 1 being a view in elevation, whereas that of Fig. 2 is a plan view.

Fig. 3 is a view depicting schematically, the location of the bow-winches on a dredgentogether with the control therefor, which encompasses the important features of my invention Figs. 4, 5, and 6 are views illustrating the mechanical construction of-a bow-winch, Fig. 4 being a plan view, Fig. '5 being a view in side elevation with a small sectionbroken away to disclose a foot brake forming a portion of the apparatus,

Fig. 6 constituting an end elevational view of the bow-winch construction with the motor removed.

In general, my invention resides in employing a pair of bow-winch devices, separately positioned, one at each side of a dredger, and intercontrolled by means of electrical control devices and circuits to simultaneously control the relative operation of said bow-winch devices.

Each winch is driven by an electric motor, which in turn is supplied from a generator individually associated with the motor. The generators are driven simultaneously and at the same speed from a common motor, which receives excitation from any convenient electrical power supply source, which ordinarily might constitute the power lines of a utility company.

One of the motors and associated generators is employed in driving one of the winch drums to reel in on the bow-line associated therewith, in

order to promote movement of the dredge in one direction. Movement of the dredge in the desired direction, in response to the operation of the reeling in motor, results in the dredger exerting a pull on the bow-line or cable connected to the winch located atthe other side of the dredger, its eflect being to unreel that cable in accordance with movement of the dredger, and accordingly drive its associated winch-drum and motor in reverse. The rotation of the motor, therefore, being reverse to that which it normally will take when permitted to operate as a motor, a retarding force is developed, whereby the motor will act as an elastic braking force, tending to retard the movement of the dredge; and at the same time the energy imparted to it in rotating its armature in a direction contrary to its normal tendency.

of rotation, is devoted to generating electrical power. The motor, now acting as a generator, will feed electrical energy to its normally associated generator and ultimately reduce the power consumption from the power lines.

In other words, as one motor functions, as such,

to drive one of the winches to produce movement of the dredger, the other motor operates as a generator, and while acting as a generator, it not only supplies the braking effect necessary to retard movement of the dredge and thereby control its rate of shift and maintain the proper tautness of its associated cable, but also feeds electrical energy back to the power supply source,

to effect a savings in the power consumed in operating the winch apparatus.

Analyzing the operation of the winches from another angle, they may be considered as simulcitation to the windings of the electrical rotating maglsiinery associated with the bow-winch appara For a more detailed description of my invention, reference will be made to the drawings. In

' Figs. land 2, I'have disclosed very schematically,

a dredger comprising 'a hull l on which is mounted all the apparatus necessary for dredging the gravel deposits and separatingout the coarserelements, leaving a mixture of gold and the liner sands for further processing.

The apparatus for accomplishing these steps, comprises a ladder I mounted ahead .of the hull and supporting thereon a bucket-line 5 adaptedto scoop up the sand or gravel and convey it to a point at some elevation above the deck, this elevation running approximately 35 or 35'feet in actual practice. At this point, the buckets'in tipping, drop their contents into a hopper 9 located adjacent the bucket-line, this hopper serving to guide the gravel to a revolving cylindrical screenll of-some length extending toward the rear of the dredge at an elevation approximately that of the hopper I which feeds it. The screen drops at an angle of about 1'7 from the horizontal, thus causing the larger components of the gravel to gradually work their way toward the rear end of the screen, from which they drop into another hopper i3, located at a point of vantage to receive this discarded material. The mixture of the gold particles and the nner sand and gravel, drops through the screen to riiile boards l5 located just below the screen, where the gold is separated out by amalgamation withmercury confined in small pools over the surfaces of the riiiie boards. In the meantime, the coarser elements which have been discarded into the hopper l3 at the rear of the dredge are guided to a stackingmechanism l6, which conveys the discard rearwardly of the dredge, where it is piled.

The dredge is spiked at some'point at the rear thereof by coupling it to a spud or pile I! which has been driven into the bed of the stream for the purpose, which spud or pile is utilized as a point about which the dredge may be swung or pivoted, the actual swinging of the dredge bein under the control of the bow-winch apparatus,

which in the preferred embodiment of my inven-- tion involves a pair of similar bow-winches l9 and 21 on the deck of the dredger, one on either side thereof. Cables or bow-lines 23 and 25 attached, one to each of the winches, have their other extremities affixed to some convenient point on the, dredger. In order that the pulling effect of the winch may be translated into a force to direct or cause movement of the dredge with respect to shore, each of the bow-lines or cables is 7 passed through a pulley or sheave 21 and 28 respectively, or similar device, which is anchored to a stake 29 and 30 respectively or other .flxed object on shore, or at some other point, to one side of the dredge. By connecting both cables in a similar manner, except that one cable passes through a pulley anchored off to one side whereas, the other cable passed through a pulley shifting of the dredge in either direction along an arc, of which the spud i1 constitutes the center, may be obtained. The bucket line is made vertically adjustable by providing a'block'and tackle 22 to support the digging end of the bucket line from a boom 24 securedto the hull of thedredgen- This permits adjustment as to the depth to which the bucket line may operate. In accordance with the preferred embodiment of my invention, each of the bow-winches I9 and II is mechanically coupled to a driving motor 3i and 33 respectively which, in turn, receives its excitation from a generator 35 and 31 respectively,'the generators associated with the respective motors for both winches, being mounted on a common shaft 39 to assure constant speed of both generators. The motors 3i and 33 and generators 35 and 31 are of the direct current type, having fields ll, 43, I5 and 41 respectively, which are separately excited from an exciter bus 49 anchored oil? to the other side of the dredger,v

which may constitute the output of a separate exciter or generator 40 driven from the shaft 39. In each of the lines to the field windings 4|, {3, l5 and of the various electrical rotating devices, is connected arheostat or variable resistance device SI, 53, and 51 respectively, to provide adjustable control of the excitation currents to these various field windings. The rheostats ii and 53, each connected in a circuit of the field winding of one of the motors, are mechanically tied in, by suitable linkage means 60, with the rheostats ii and 51, respectively, of one of the generators, to assure that both windings will receive excitation, and in proper amounts simultaneously.

Switches 59 and 6| of the double-pole, doublethrow type, each connected in a circuit to the field winding of each generator, provide convenient means for selectively reversing the field winding of each generator at will, the purpose of which will be described hereafter.

Since the type of electrical energy to be obtained from power lines of the various utility corporations, is customarily of the three phase alternating current type, the shaft 39 upon which the direct current generators are mounted, is driven by a three phase alternating current motor 61, it being understood, of course, that where the incoming power energy is of a single phase or of a different character than three phase energy, the generator driving motor will be changed accordingly.

In series with each of the main windings l and of the direct current generators 35 and 37, there is connected an independently, manually adjustable rheostat. 69 and H respectively, in order to permit adjustment of the main field of each of the direct current generators selectively, and independently of the motor which that generator is supplying with energy, it being noted that the main rheostat in the field circuit of each direct current generator is mechanically coupled -to the rheostat in the field winding of its associated motor. 5 a

In theoperation of the electrical control thus described, the mechanically coupled rheostats 5| and 55 of one of the motors 3| and associated generators 35 are adjusted sons to provide sum-.- cient excitation to both the generator and the motor to develop the necessary torque to operate the winch-drum l9, and cause it to take up or this retarding force is obtained by applying a lesser amount of excitation to the motor 33 and generator 31 positioned on the other side of the dredge, these being so adjusted with respect to direction of rotation, that the winch 2| driven hereby, will have a torque applied thereto tend ng to rotate it in a direction opposite to that of the first winch. This tendencyto rotate in the opposite direction, however, is overcome by the aforementioned pull of the cable 25 against the winch, produced by movement of the dredge in the desired direction, this pull being in such direction as to result in unreeling of the cable.

from the drum of the second winch in accordance with movement of the dredger, and producing rotation thereof in a direction, the reverse of that in which the winch 25 would rotate were no pulling effect exerted thereon. The result of the action just described is to efiect a retarding force on the movement of the dredge in the desired direction, and this retarding force can be adjusted as to magnitude, by controlling the field intensity of both the motor 33 and the generator 31 associated therewith; Adjustment of the retarding foroethus provides a very convenient and satisfactory means for controlling the rate of movement of the dredge.

At the same time, the motor 33, which is meerating energy, while operating to exert a retarding effect is termed regenerative braking, and results in cutting down the total power consumed by the winch apparatus in providing and controlling movement of the dredge.

In actual operation, the torque applied to any one of the winches i9 or 2| may be controlled at the generator end by independently adjusting the auxiliary rheostat 69 or II connected in series with the main field winding of the generator. The resistance range of this independently actuated rheostat may be made large compared to the one which is mechanically coupled to the motor rheostat, to enable an operator to obtain a rough adjustment of the torque range of the winch driving motor to obtain satisfactory opera tion under different ground conditions, the finer torque adjustments being obtainable through adjustment of the mechanically'coupled rheostats.

An ideal torque curve for dredger apparatus of the character described above, would be one wherein the speed of the driving motors remains substantially constant for all loads up to the maximum permissive load and then drops suddenly to zero speed, which constitutes a stalling of the motor. This type of torque characteristic is approached by incorporating a selfexcited field winding 45 and a series winding 63 in one of the'direct current generators.35, the series winding being connected in opposition to the others, Corresponding shunt winding 48 and series winding 65 are incorporated in generator. 31. Without the shunt winding on-the generator, the speed of the motor would begin to drop as load. was applied and would gradually decrease from a maximum speed at zero torque to a stalled condition at maximum torque, which would not be satisfactory for dredger operation;

wherein it is desirable that the speed of the driving motor remain substantially constant during normal working loads. The shunt field in addition to the series field is essential in obtaining the proper torque characteristic.

While a reduction in torque could be realized by differentially compounding the motor instead -of the generator, the desired torque characteristic could not conveniently be obtained in this manner. The speed of the motor would gradually diminish inversely with the increase in torque developed to take care of a varying load. The

desired constant speed characteristic would not be obtained.

In referring to the retarding or braking action of the winch, I have characterized it as being an elastic retarding force. By this expression, I mean to bring out the fact that while the pull of the cable 25 for example, on that particular winch-drum 2| produces rotation in such a direction as to cause the motor 33 to act as a generator, there nevertheless always exists a torque on the winch-drum tending to rotate the winch 2| in the reverse direction. This torque exists by reason of the application of limitedfield excitation to the motor 33 and generator 31 while this winch and motor are functioning as the'braking mechanism. As long as the dredge is being shifted in the direction determined by winch IS,

the pulling effect of the cable 25 on the drum of the second winch 2| is of a greater magnitude I than the torque eflect mentioned, but the magas having the property .of elasticity, which a mechanical friction brake does not possess. Another advantage attributed to this characteristic of the braking effect, is that there is always a tendency of the braking winch to reel up or take up on any slack which may, for any reason, tend to develop in its associated cable. Such a .condition may arise inthe event of accidental breakage of the other cable.

The braking action, due to this aforementioned elasticity characteristic, furthermore, give with sudden applications of load to the driving motor and thereby tend to iron outthe sudden changes in stresses in the cables which might otherwise'result ina breaking of the same,.particulariy if in a partially worn condition.

While the operation of the above system has been describedwith reference to the use of one of the winches l9 as the driving or reeling-in element to produce shifting of the dredgein one desired direction, it be apparent that similar operation will obtain, when movement of ,the dredge in the opposite direction is desired, the

only difference being'that the winch 2| and associated electrical apparatus 38, 31, etc., which has I previously operated to supply the braking or retarding force, will now operate as the driving apparatus, and the other winch I8 and its associate apparatus, 31, 35, etc., which had previously operated as the driving apparatus will now operate to produce the retarding or regenerative brak ing effect.

The specific construction of each of the winches and driving motor is disclosed in detail in Figs.

; 4, 5 and 6, to whichreference will now be made' in describing this apparatus. The motor ii, for example, mounted on suitable bearings. is connected mechanically through a speed reduction gear, encased in a housing 18, to the active element 15 or the power end of a clutch mechanism; the other portion of the clutch being in the form of collar 18 slidably keyed to a power transfer shaft 8i and normally engaging the power end 15 of the clutch. The power transfershaft is supported in suitable bearings and is provided with a pinion gear 83 which is in constant mesh with a spur gear 85 of considerably larger diameter. This spur gear is fixedly attached to one side of a winch-drum 81, which-is also supported-onbearings and by reason of the mechanical coupling between the drum 81 and the driving motor 3| which includes the various gears mentioned, the drum is adapted to berotated, at a reduced speed by the motor.

The aforementioned clutch, which is normally ing the driving motor 31 from the winch-drum 81,

permitting it to rotate more or less freely on its own bearings. The lower end of the clutch lever 88 is notched for engagement with a spring catch 88 to hold the clutch in either its open or normally engaging condition.

Freedom of rotation of-the drum when disengaged from its driving motor may be impeded at will through the expediency of a foot brake, which comprises a, foot lever 83, located on the same side of the winch apparatus as the clutch control lever 89 and having its foot-engaging element 95 in the vicinity ofthe clutch operating lever so that they may both be within the control of a single operator. The foot lever is connected toward the front end of the winch to a rocker shaft, 91, the angular rotation of which is opposed by a spring 2. Movement of the foot lever is, constrained to vertical motion by guide 89 connected to the frame of the winchdrum and notched to one side of the lever to efiect a locking engagement therewith, to maintain a desired braking adjustment of the foot brake.

The braking element comprises a brake shoe I I8! adapted to frictionally contact an edge I83 of the drum, which edge is of suilicient width for the purpose, and is adjustable with respect to this edge of the drum by means of a short, threaded shaft N15 to one end of which it is pivoted.

of the rocker shaft opposite that end to which the foot lever is attached. Afterproper adjustment of. the brake shoe with respect to the edge of the drum, it is locked in place at the end of the crank lever.

The brake shoe is not only supported by its pivot connection to the threaded adjustable shaft,

but also receives additional support from a link Hi9 which is rigidly connected thereto at one end and supported pivotally at its other end by a bracket Ill attached to-the frame which supports the drum.

The motor is provided at that end which is not connected to the gear train, with a magnetic brake to maintain a fixed position of its armature and consequently a fixed position of the winchdrum, when the electrical power to the motor is disconnected.

.This brake is adapted to frictionally engage a drum H3 coupled to themotor shaft and is normally held out of engagement by an energized solenoid ill attracting one end of a lever "1 to the other end of which is attached a brake band H8 in position to be clamped against the brake drum ill. The energized solenoid maintains the lever in its up position against the action of a strong spring I, which when free to act (when solenoid is de-energized) 'pulls the lever to a down position, in which position, the brake band is clamped against the brake drum to effect braking action.

The cable or bow-line is affixed to the winchdrum by means of any suitable clamping mechanism I23 and thereafter is adapted to be wound up on the drum, upon rotation of the same by the driving motor in the proper direction.

The manually controllable clutch and the footoperated brake and the magnetic brake described above in connection with the. winch mechanism,

are not employedduring normal operation of the bow-winch apparatus in eflecting desired shifting of the dredger, and insofar as this normal operation of the dredger is involved, these elements might be dispensed with. However; these feaend of the oldcable is attached to a tractor or tures are of some importance and find useful application, when it is desired to replace a cable or if it is desired to maintain the dredge in any fixed position with the electrical power disconnected.

When it is desired to replace a cable, the loose other motive vehicle on shore, and unrolled from the winch-drum. In order to protect the motor armature from the excessive rotational speed to which it would be subjected as the cable was being unwound from the winch-drum, the motor is disengaged by means of the clutch connecting it direction by the motor. During the process of winding the cable, it may become necessary to unwind a certain stretch of cable now and then in order to obtain proper alignment and seating thereof on the drum. The drum is capable of being reversed at will through a reversal of the motor, which is accomplished by reversing the separately excited field of the generator which supplies energy to that motor. The double-pole, double-throw switches 59 and 6i provide the means for reversing the fields of their respective generators.

The purpose ofthe magnetic brake has already been described as constituting a means for automatically setting the position of the dredger at such times as when the power is disconnected from the winch mechanism. This result is, of course, accomplished by clamping the motors against rotation and consequently transmitting the braking effect through to the winch drums. The electrical excitation to this brake, it will be noted, is employed-not to supply the braking force but to maintain the brake in its open or "nonbraking condition. The actual braking efiort is supplied mechanically by means of the spring i2i. While this means that the brake will receive excitation continually as long as the winch mechanism is in operation, nevertheless, in the event of failure of the power supply, a braking-force is assured and will automatically assertitself. And

during periods of rest when the men are off the Job, these brakes will continueto stabilize the position of the dredger without relyingupon power power lines to maintain this supplied from the status.

It will beapparent in the above detailed description of my invention that it fulfills all the objects and advantages attributed to my invention, and provides improved and more economical operation over what has been previously realized in connection with bow-winch appa atus of the type constituting prior art. Y 7

It has been found that a dredger embodying my improved bow-winch control apparatus enables a decided increase in overall emciency, over the old type of apparatus, and this can be traceable to the savings in power through the ,use of regenerative braking; the lack of repairs and replacements, which were formerly involvedin the use of mechanical frictional braking, and to the absence of periodic shut-downs and loss'of time attributable to the same cause, namely, the use of frictional apparatus for braking purposes.

The increase in efficiency of dredging, attributable to my improved bow-winch and control, appal ratus has made it profitable to extract gold from deposits, which heretofore, could not be worked advantage.

I claim: v i

1. Means for exerting opposed controllable forces and for making either one greater than the other, comprising: an electrical driving motor; direct current generators driven by said motor; a

direct current motor driven by one of said generators; a direct current motor driven by another of said generators; said motors driven by said generators exerting opposed forces simultaneously upon the same movable object; and means to increase the torque of either of said direct current motors as desired over that of the other to make either of said opposed forces the greater and the direct current motor having the lesser torque function to brake the movement of said object whereby the energy consumed by said driving motor tends to be increased, said motor having the lesser torque tending to function as a generator to drive the generator of its set as a motor whereby the energy consumed by: said driving motor tends to be decreased.

2. Means for exerting opposed controllable forces and for making either one greater than the other, comprising: an electrical driving motor, direct current generators driven by said motor; a

direct current motor driven by one of said generators; a-direct current motor driven by, another of said generators; said motors driven by said, generators exerting opposed forces simultaneously upon the same movableobject; means to increase the torque of either of said direct current motors as desired over that of the other to control the direction of movement of said object and to make the direct current motor having the lesser torque function t9 brake the movement of said object whereby the energy consumed by said driving motor tends to-be increased, said motor having the lesser torque tending to function as a genera tor to drive the generator of its set as a motor, whereby the energy consumed by said driving motor tends to be decreased; and means to control the degree of torque difierentialto control the speed of movement of said object.

3. A dredging apparatus comprising a hull or the like, meansto pivotally hold said hull at one end thereof, an adjustable train of scoops at the other end thereof, c'able positioning means fixed in position independently of and at each side of said hull, cables, and means .on said hull for differentially pulling said cables to swing the other end'thereof in either direction about said pivotas a center, comprising: a pair of winches, a pair of direct current ,motors each connected to a winch, a pairof direct current generators each to drive one of said'motors, a prime mover motor, a field exciting generator, said prime mover motor and said generators being mounted upon the same rotatable shaft to have the same speed of revolution, each said direct current motor and its respective generator having a field excited by said exciter, said generators to drive said direct current motors having in addineously vary the fields excited by said exciting -generator of a direct current motor and-of. its

respective generator, means to a independently vary said fields of said generators for saiddirect I current motors, brakes normally tending to pre-W vent rotation of said winches, and means opera ative by electric power and inoperative on. failure 1 4. In combination, a structure, the position of which is to be shifted to perform work during the shifting thereof on material which is apart from said structure, means capable of exerting a plurality of positive forces on said structure, tending to shift said structure in opposite directions, said means comprising a plurality of motors supported on said structure, each exerting a force thereon through a mechanical power transfer link extending through a point which is fixed against movement, means for determining a desired unbalanced condition of said forces to obtain shifting of said structure in a given direction, comprising a plurality of mechanically coupled generators, each generator being electrically connected to supply voltage to one of said motors, and independently adjustable field excitation for each of said'generators.

5. A gold mining dredge or the like apparatus of the character in'which operating mechanism thereon is adapted to work on material presented to the mechanism while the dredge is oscillated back and forth, winch mechanism on the dredge to which a cable anchored of! of the dredge is connected for pulling the dredge in one direction, another winch mechanism on the dredge to which a cable anchored off of the;

dredge is connected for pulling the dredge in an opposite direction; and means on the dredge for correlating the operation of the winch mechanisms and enhancing the operating efficiency thereof comprising: a separate electric motor to rotate each winch to wind the respective cable thereon, a separate electric generator to drive each motor, said generators being rotatably interconnected, and means to vary the relative forces exerted by said motors to cause either winch to exert a stronger pull than the other and thereby cause said dredge to move in a chosen direction and said other winch to rotate to unwind its cable and to cause the motor connected to said other winch to generate and feed current to its driving generator which thereby becomes-a driven motor to lessen the power required for the operation of the other generator.

LELAND S. ROSENER. 

